This invention relates generally to injection molding and more particularly to apparatus wherein nozzles extend diagonally from an elongated manifold to convey melt to gates extending parallel to the parting line.
Injection molding simultaneously through a number of gates to a number of different cavities is well known in the art and is referred to as multi-cavity molding. It is well known to do this using a number of hot tip gated nozzles to convey melt out from a common melt distribution manifold or using a single edge gated nozzle to convey melt to a number of surrounding gates. Examples of edge gated nozzles are shown in the applicants' U.S. Pat. No. 4,344,750 which issued Aug. 17, 1982 and in FIG. 4 of U.S. Pat. No. 5,217,730 to Teng which issued Jun. 8, 1993. These configurations have the advantage that the gates extend parallel to the parting line or perpendicular to the direction of mold opening and thus provide very clean shearing at the gate when the parts are demolded from the cavities. However, in addition to not being hot tip gated, they have the serious disadvantage for many larger cavity applications that the gates must be located relatively close together around the single nozzle between them. This space restriction limits the extent and location of cooling which can be provided adjacent the cavities which is important for fast cycles. It also limits the position of the gate on the cavity which is important in other situations to avoid undue core shift.
An example of a number of hot tip gated nozzles extending out from a common melt distribution manifold is shown in U.S. Pat. No. 4,768,945 to Schmidt et al. which issued Sep. 6, 1988. While avoiding the above disadvantages of edge gating, this configuration has the disadvantage that the hot tip gates cannot be oriented to extend to a portion of the cavity wall which is perpendicular to the parting line to produce the shearing effect of edge gating. An example of nozzles extending diagonally outwardly from a common manifold is shown in FIG. 28 of Plastverarbeiter Volume 30 Number 2, 1979 pages 83-88 but it similarly has the disadvantage that the gates cannot extend parallel to the parting line and must be positioned at an angled portion of the cavity wall. Page 7 of Mold-Masters Limited Brochure E-CMSSN-11-90 Injection Molding with Compact Master-Shot shows nozzles for both angled hot tip gating and angled edge gating. However, none of the prior art shows the combined advantages of hot tip gating and shearing at the gates provided by the gates being oriented perpendicular to the direction of opening of the mold.